The energy infrastructure of the world depends on pipelines. Pipelines transport crude oil and unrefined gas from wells to refineries and transport refined products to chemical plants, utilities, local distribution units, homes, airports, and nearly every place that uses energy. Energy pipelines include liquid petroleum pipelines and natural gas pipelines.
Pipelines can vary in size depending on purpose. For example, in oil-producing locations, gathering pipelines may be as small as two inches in diameter. The Trans-Alaska Pipeline, in contrast, which transports crude oil, is about 48 inches in diameter. Pipelines of varying sizes and purposes have diameters in between.
Given the materials being transported, pipelines present health, safety, environmental, and security concerns. Pipeline and energy companies are economically incentivized to bring as much product as possible from source to destination. The various governments also regulate pipelines and pipeline-transported materials extensively. To prevent release of pipeline-transported materials, pipeline and energy companies conduct integrity management programs continuously.
Integrity management programs include inspections to determine the integrity of pipeline systems. To this end, inspections may identify early indications of future problems, such as corrosion, cracks, mechanical damage, and dent and bend strain locations that may have defects that can cause failures in the future. Pipeline inspection companies have developed specialized tools to inspect the full body of pipelines, including inline inspection tools commonly referred to as smart pigs.
Smart pigs travel through the interior of a pipeline, often without stopping the flow of medium through the pipeline. These pigs may collect gigabytes of data about a pipeline including wall thickness, geometrical shape, corrosion, pitting, cracks, holes, dents, and other potential sources of problems. Identifiable flaws include, but are not limited to, metal loss caused by corrosion, erosion, pipe manufacturing, and construction of pipelines. These flaws may also include some forms of axially oriented flaws, such as narrow axial metal loss, hook cracks, lack of fusion, and fatigue-related cracking. These flaws may also include circumferentially oriented flaws of a similar nature. Mechanical damage may also be identified, including dents, gouges, cracks, and combined defects (e.g., a gouge near a pipe seam), and these types of damage may also be oriented either axially or circumferentially. Pigs use various, specialized sensing systems to automatically and continuously collect and store this data. Related software is typically used to interpret the data and aid operators in identifying significant flaws in order to investigate and make the necessary repairs to help prevent failures.
Pigs used for in-line inspection of pipelines may employ one or more of several technologies, including but are not limited to ultrasonic technology (“UT”) for wall thickness measurements or crack detection, electromagnetic acoustic transducer (“EMAT”) technology, magnetic flux leakage (“MFL”) technology, pipe surface profiling commonly referred to as geometry or caliper technology, and inertial mapping of pipe locations and detection of ground movement (“IMU”). MFL is a nondestructive method of testing that employs a magnetic flux leakage principle to detect certain defects and potential problems found in the full body of a pipeline. MFL can be used only in pipelines made of ferromagnetic metals, such as carbon based steels. Powerful magnets, including permanent or electromagnets, magnetize portions of the pipeline, and sensors may be generally placed between the poles of the magnets to monitor the changes in flux leakage from the pipeline in areas experiencing various flaws where the cross sectional area is reduced by metal loss or where a fissure or crack perpendicular to the direction of the magnetic field causes a detectable change in the magnetic leakage field. Automated feature searches and human analysis can provide comprehensive reporting, prioritizing, and quantifying the severity of flaws. This information is then used by the pipeline operators to facilitate field investigations, repairs, and future inspection intervals.